Backhoes and front loaders are work vehicles that engage in digging and moving materials around construction or other work sites. As a part of this work, they often drive into piles of material, scoop up a portion of those piles using a front loader or a rear backhoe, then reverse their direction to convey the scooped material to a new location a short distance away. This activity requires the vehicles to frequently change their direction of travel, such that the operator frequently shifts from a forward direction of travel to a reverse direction of travel and vice-versa. In addition, these vehicles are also rapidly and alternatively loaded and unloaded, producing large fluctuating loads. As a result of these job requirements, the vehicles are often equipped with transmissions having torque converters that reduce the potential drive train damage that might appear if manual transmissions were used. In addition to and complementing the torque converter, these vehicles can also include a shuttle shift lever that allows rapid shifting between forward and reverse. The shuttle shift lever typically operates by selectively and alternatively connecting forward and reverse hydraulic circuits on the transmission that place the transmission alternatively in forward and reverse. Since these levers are operated rapidly and frequently, they can on rare occasions simultaneously send out command signals indicative of more than one desired mode of operation, typically signals indicative of a forward shift command and a neutral shift command, or signals indicative of a reverse shift command and a neutral shift command. This can happen, for example, when the operator holds the shuttle shift lever halfway between a forward position and a neutral position or halfway between a reverse position and neutral position. The application of these two pairs of incompatible signals (forward and neutral or reverse and neutral) can leave the vehicle's transmission in an unknown state. It is a goal of the present invention to provide a vehicle having a transmission control circuit that prevents such incompatible signals from leaving the vehicle's transmission in an unknown state.